Chemical weapons inspectors have collected samples from Syria’s Douma, two weeks after a suspected gas attack prompted retaliatory strikes by Western powers on the Syrian government’s chemical facilities.

Chemical weapons inspectors have collected samples from Syria’s Douma, two weeks after a suspected gas attack prompted retaliatory strikes by Western powers on the Syrian government’s chemical facilities.

The site visit, confirmed by the Organisation for the Prohibition of Chemical Weapons (OPCW), would allow the agency to proceed with an independent investigation to determine what chemicals, if any, were used in the April 7 attack that medical workers said killed more than 40 people.

Douma was the final target of the government’s sweeping campaign to seize back control of the eastern Ghouta suburbs of Damascus from rebels after seven years of revolt. Militants gave up the town days after the alleged attack.

The Damascus sky was lit up missile fire from the US-led attack (Hassan Ammar/AP)

The US, France, and Britain blamed President Bashar Assad’s government for the attack, and struck suspected Syrian chemical weapons facilities one week later.

The Syrian government and its ally Russia denied responsibility for the attack.

OPCW inspectors arrived in Damascus just hours before the April 15 strikes but were delayed from visiting the site until Saturday, leading Western officials and Syrian activists to accuse Russia and the Syrian government of staging a cover-up.

The OPCW said in a statement that it visited “one of the sites” in Douma to collect samples for analysis at agency-designated laboratories, adding it would “consider future steps including another possible visit to Douma”.

It said the mission will draft a report based on the findings, “as well other information and materials collected by the team.”

The OPCW mission is not mandated to apportion to blame for the attack.

A UN security team had scouted Douma to see if it was safe for weapons inspectors to visit (Bassem Mroue/AP)

A UN security team had scouted Douma on Tuesday to see if it was safe for weapons inspectors to visit. The team came under small arms and explosives fire, leading the agency to delay its mission.

Russian ministry spokeswoman Maria Zakharova said the delays to the OPCW team were “unacceptable”.

Images emerging from Douma in the hours after the attack showed lifeless bodies collapsed in crowded rooms, some with foam around their noses and mouths.

Raed Saleh, the head of the Syrian Civil Defence search-and-rescue group, also known as the White Helmets, said his organisation had shared the coordinates of the graves of the April 7 victims with the OPCW, so that inspectors could take biological samples.

Civil Defence workers evacuated Douma after the attack, fearing persecution by the security services of the government. The government says the group is a terrorist organization.

Douma was the site of a suspected chemical weapons attack (Hassan Ammar/AP)

Thousands of people — rebels and civilians — left Douma on buses to north Syria in the days after the attack, believing they could not live under government authority after it retook the town. North Syria is divided between opposition, Turkish, and al Qaida control.

The evacuations were the latest in a string of population transfers around the Syrian capital that have displaced more than 60,000 people as the government reconsolidates control after seven years of civil war.

UN officials and human rights groups say the evacuations amount to a forced population displacement that may be a war crime.

On Saturday, rebels began evacuating three towns in the eastern Qalamoun region in the Damascus countryside, state TV reported.

State-run Al-Ikhbariya TV said 35 buses left the towns of Ruhaiba, Jayroud, and al-Nasriya carrying hundreds of rebels and their families to opposition territory in north Syria.

The station said up to 3,200 rebels could leave the three towns on Saturday in evacuations lasting three days.

Syrian government forces will take over the towns once the departures are complete.